• What is hyperthermia?
• How does hyperthermia work?
• What patients are candidates for hyperthermia?
• What is the hyperthermia treatment process?
• What are possible side effects of hyperthermia treatment?

What is hyperthermia?

The word hyperthermia means "elevated body temperature" and in a medical context refers to the use of heat in the treatment of disease. The idea of using heat to shrink tumors is documented in records that date back to the early Egyptians and ancient Greeks. It was not until recently, however, that body temperatures could be raised in an effective and safe manner. Exactly how hyperthermia works is complex and still under investigation, but clinical research has demonstrated that hyperthermia both causes tumor regression on its own and increases the sensitivity of tumor cells to radiation and chemotherapy.

The main forms of hyperthermia used in patients with cancer currently fall into three categories: whole-body systemic hyperthermia, regional hyperthermia and local, site-specific hyperthermia. Most clinical experience has been with local hyperthermia in the treatment of superficial tumors 1 to 8 centimeters from the surface of the skin. Treating tumors deeper than 8 centimeters is complex, and appropriate techniques are still evolving.

Local or regional hyperthermia treatment most often involves the use of ultrasound, microwaves or radio-frequency (RF)-induced currents to raise body temperatures at a specific site. The temperature range achieved is 41-45 degrees Celsius or 106-113 degrees Fahrenheit, similar to a hot bath.

At PAMF, all hyperthermia treatments are administered by ultrasound and aim to maintain a temperature of about 42.5 to 43 degrees Celsius for 60 minutes. Approximately three to eight treatments are given immediately before or after radiation. The number of treatments depends on a variety of factors, including the amount of surface area involved. Each hyperthermia treatment is separated in time by at least two days to prevent tumors from developing resistance to the heat.

PAMF’s hyperthermia suite was started in 1992 with a $2.1 million endowment from the late Atherton publisher Michael Kilbane, in memory of his wife, Etta Kilbane. "The Kilbanes’ endowment subsidizes the procedure, technical staff and equipment. It would be difficult, if not impossible, to maintain the hyperthermia suite without the endowment," said Gordon Ray, M.D., head of the Radiation Oncology Department.

In the United States there are approximately 250 centers that perform hyperthermia. In the Bay Area, PAMF and the University of California at San Francisco (UCSF) are the only medical centers offering hyperthermia, and patients are frequently referred to PAMF from outside clinics.

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How does hyperthermia work?

Cancer cells are different from normal cells in many ways, including their responses to heat. In most cases, these differences make it possible for hyperthermia to kill cancer cells without significantly harming normal tissue surrounding the tumor.

Hyperthermia damages the tumor’s blood vessel structure and causes other changes in tumor cell function. These effects are enhanced in hypoxic (oxygen-deprived), highly acidic environments. Tumors are often more hypoxic and acidic than normal tissues, which may also partially explain why hyperthermia can damage cancer cells while leaving healthy surrounding tissue largely intact.

Although hyperthermia alone is damaging to tumors, it is most effective when used in conjunction with radiation therapy and, to a more limited extent, with chemotherapy. When used in combination with radiation therapy, hyperthermia makes it more difficult for tumor cells to repair radiation-induced damage. It also makes certain cells that are normally resistant to radiation more sensitive to the therapy.

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What patients are candidates for hyperthermia?

Not all tumors are suitable for hyperthermia treatment. Factors such as the tumor's heat sensitivity, depth and location can limit use of the therapy. Generally, patients should meet the criteria below to be eligible for hyperthermia.

• The cancer is usually recurrent or advanced, so that adding hyperthermia to radiation therapy offers a therapeutic advantage over radiation alone.


• The cancer must be located within several centimeters of the skin surface.


• Patients must be able to lie relatively flat for at least an hour.

The following types of cancers are treated with hyperthermia at PAMF:

• Breast cancer


• After mastectomy with a recurrence of cancer in the chest wall


• Local or regional recurrence of cancer


• Advanced primary breast cancer


• Malignant melanoma (skin cancer)


• Sarcomas (cancer in the bone, muscle or soft tissues)


• Lymphomas


• Head and neck cancers


• Other selected cancer types

Patients should discuss with their radiation oncologist whether hyperthermia would be appropriate.

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What is the hyperthermia treatment process?

Your hyperthermia treatment program will be planned and managed by your radiation oncologist and a technologist in PAMF’s Etta Kilbane Hyperthermia Suite.

Hyperthermia is given immediately before or after radiation therapy, in order to best maximize tumor sensitization while protecting skin. Each hyperthermia treatment lasts approximately one hour. Including the time required for set-up and radiation therapy, patients should allow about 2.5 hours at the Clinic for each hyperthermia treatment. Since patients will be in the hyperthermia suite for most of that time, we recommend they use the restroom and avoid liquids prior to therapy.

Prior to treatment, one or two tiny needle thermometers (known as thermocouples) will be inserted into the treatment area after it has been numbed with a local anesthetic. These thermometers allow the physician and hyperthermia technologist to gauge the temperature inside and around the tumor in order to properly control treatment. In addition, several external sensors will be placed on the skin to measure surface temperatures. The treatment area will then be covered with an ultrasound gel.

During treatment, the hyperthermia technologist will monitor the temperature sensors and heat patterns. Minor adjustments may be made in the positions of the temperature probes or ultrasound applicator to ensure optimal and uniform heating throughout the treatment area.

Patients may feel a sensation of heat that causes minor discomfort during therapy. Our goal is to heat the tumor as effectively and evenly as possible without making it too hot or uncomfortable for the patient. Therefore, if patients experience any pain during treatment, we ask that they let us know so that power input, applicator placement or body position can be adjusted.

The duration of hyperthermia treatment and the time between treatments are important variables. If heat is administered too long or too frequently, tumor cells can develop resistance – a phenomenon called thermotolerance. To prevent thermotolerance, hyperthermia treatments are typically separated by at least 48 hours.

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What are possible side effects of hyperthermia treatment?

• Discomfort: The most common side effect of hyperthermia treatment is a sensation of warmth and discomfort during treatment, which can be managed with pain medications prior to or during hyperthermia if needed. In addition, there may be some tenderness at the probe insertion sites for a couple days following treatment.


• Fat necrosis: Hyperthermia carries approximately a 5-10% chance of developing a condition called “fat necrosis,” which can leave a hardened area of tissue or lump(s) under the skin and is usually permanent. Areas of fat necrosis are typically tender at first; however, the tenderness almost always goes away. These areas are not cancerous and can be biopsied for reassurance.


• Other side effects: Less commonly, blood pressure fluctuations, blisters on the skin, superficial ulcers, bleeding or infection may develop after hyperthermia.

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